Measuring and testing – Vehicle chassis – Steering
Reexamination Certificate
1999-12-20
2001-12-11
Dombroske, George (Department: 2855)
Measuring and testing
Vehicle chassis
Steering
C701S030000
Reexamination Certificate
active
06327900
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the monitoring of engine oil in a motor vehicle and, more particularly, to a method for advising an operator of the need to change the engine oil in a direct or an indirect injection diesel engine based on oil temperature and oil contamination.
BACKGROUND OF THE INVENTION
It is known in the art relating to automotive vehicles that engine durability is directly related to the lubricating ability of the engine crankcase oil, and that its lubricating ability becomes degraded with engine operation and time. Thus, most engine and vehicle manufacturers provide their customers with oil change maintenance schedules for the point at which the engine oil should be changed. These oil change maintenance schedules are only guidelines and, depending on the engine operating conditions, the required oil change interval may be less than 3,000 miles or greater than 10,000 miles. To provide a more accurate prediction of the point at which the oil should be changed, an estimate of the extent of oil degradation and the need for an oil change for a given vehicle can be determined by electronically monitoring certain key engine operating parameters in the course of vehicle operation between oil changes. When it is determined that an oil change is required, the operator is so informed by an instrument panel indicator.
It has been shown that a direct and accurate indication of engine oil degradation can be determined by assessing two effects: (1) chemical changes that occur as a consequence of exposure of the engine oil to high or low temperatures, without regard to engine loading or other operating conditions which may only be indirectly related to oil temperature, and (2) formation of contaminants such as soot and acids that typically are produced at high load and high temperature.
Excessive degradation of the engine oil occurs at its temperature extremes. At low engine oil temperatures, typically during start-up, fuel and water can accumulate in the engine oil. Fuel and fuel reaction products can also enter the engine oil and cause a decrease in oil viscosity. This low temperature effect can occur completely independent of the load.
At high engine oil temperatures, antioxidants in the oil can become inactivated, and thus a major additive that provides chemical stability to the engine oil is no longer as effective as it was initially. As a consequence, the oil becomes more viscous and acidic due to oxidation and nitration. In addition, insoluble materials may be deposited on the engine surfaces as a varnish or sludge.
Another type of oil degradation occurs as a function of the rate at which fuel is injected into the cylinders of the diesel engine. Contaminants such as soot and acids form during incomplete combustion, typically at high temperatures and at high loads. Soot and acids that have entered the engine oil reduce the ability of the oil to prevent corrosion and increase soot-related wear. Therefore, it is desirable to provide a monitoring system that determines the need to change the engine oil based on both the degradation of the engine oil due to high and low temperature effects and the degradation due to contamination from load-related soot and acid effects.
SUMMARY OF THE INVENTION
The invention provides a method for advising an operator of a motor vehicle with a diesel engine of the need to change the oil based on a calculated rate of engine oil degradation. The rate of engine oil degradation is affected by the temperature of the oil and the amount of contaminants entering the oil at high loads. Under conditions in which both temperature effects and high load effects are occurring simultaneously, the calculated rate of degradation takes into account both effects.
The rate of degradation of the engine oil is calculated by assessing the severity of engine operation as a function of both oil temperature and oil contamination. The severity of service due to differences in the engine oil temperature is assessed by determining an engine oil temperature value over a predetermined interval that may be measured in terms of time (for example, one second) or in terms of engine revolutions (for example, 500 revolutions) and assigning a penalty factor associated with that temperature. The severity of service due to contamination is assessed by calculating an engine oil contaminant value from various engine parameters and assigning a penalty factor for that value. In general, these relationships are established experimentally for each engine design.
The duration of each given effect is assessed by monitoring the elapsed number of engine revolutions or the elapsed time. At the start of service after a reset of the oil life monitor system, the number of engine revolutions corresponding to the maximum allowed number of engine revolutions for the useful life of the engine oil is stored in the vehicle's computer memory. In each period of vehicle operation, the stored number is decreased by an effective engine revolutions value determined in relation to the product of measured engine revolutions and the penalty factors found to be associated with engine oil temperature and engine oil contamination, resulting in a remaining allowed engine revolutions value. The penalty factors increase the effective revolutions value to compensate for engine operating conditions that tend to increase degradation of the engine oil. Each time the effective engine revolutions value is calculated and subtracted from the remaining allowed engine revolutions value, a new remaining allowed engine revolutions value is stored in memory, replacing the old value. When the stored remaining allowed engine revolutions value decreases below a predetermined threshold value, a signal is sent to the driver of the vehicle that an oil change is needed.
The engine oil temperature value used in determining the oil temperature penalty factor may be measured or calculated in one of two ways, depending on whether an oil temperature value is within a warm up range or in an equilibrium range. When the oil temperature value is below a predetermined temperature, or within the warm up range, the oil temperature is calculated from the initial coolant temperature and the number of engine revolutions since the beginning of the present engine operation. Once the oil temperature has reached the predetermined temperature, or is within the equilibrium range, the oil temperature is calculated from measurements which may include engine rotational speed, vehicle speed, coolant temperature, fuel injection quantity (per cylinder) and intake air temperature. Statistical techniques are available and in common use to smooth the calculated oil temperature curve. The engine oil contamination value used in determining the oil contaminant penalty factor is calculated from the oil temperature value, fuel injection timing (crank angle), fuel injection quantity and engine rotational speed. Again, these operating conditions are available to the engine control computer and can be used in a simple linear equation to calculate a useful contamination factor to be applied to engine revolutions occurring in the test cycle. The constants of the equation are fitted statistically for each engine type based on experimental data.
In addition, in the event the engine operating conditions are not severe enough to cause the revolutions counter to expire, the indicator will be activated when the vehicle has been driven a predetermined number of miles, or the maximum mileage recommended by the vehicle manufacturer for oil change intervals.
These and other features and advantages of the invention will be more fully understood from the following description of a specific embodiment of the invention taken together with the accompanying drawings.
REFERENCES:
patent: 4839831 (1989-06-01), Imajo et al.
patent: 5060156 (1991-10-01), Vajgart et al.
patent: 5382942 (1995-01-01), Raffa et al.
patent: 5530647 (1996-06-01), Sem et al.
patent: 5633796 (1997-05-01), Cullen et al.
patent: 5642284 (1997-06-01), Parupalli et al.
patent: 5750887 (1998-
Fletcher Scott John
Hamparian Nshan
Jacek Michael
Mc Donald John E.
Schwartz Ellen Shirley
Dombroske George
General Motors Corporation
Grove George A.
Hodges Leslie C.
LandOfFree
Oil life monitor for diesel engines does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Oil life monitor for diesel engines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oil life monitor for diesel engines will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2590758